This invention relates to nuclear reactor fuel, and more particularly to the inspection for failure of cladded nuclear fuel rods.
In modern light-water nuclear power reactors, the reactor core typically consists of over one hundred closely spaced fuel assemblies, each assembly containing an array of over one hundred individual fuel rods. The fuel rods are typically elongated, sealed tubes of Zircaloy containing a column of uranium dioxide pellets. Safe operation of the reactor requires that the integrity of the Zircaloy clad be maintained throughout the burnup history of each fuel rod. Occasionally, however, the clad is perforated during operation. Although each fuel assembly typically burns for a total of about three cycles, or about three years, the assemblies in the reactor core are usually rearranged annually during the refueling process. During refueling, the assemblies may be removed from the core and inspected for failed fuel. This inspection is typically very complicated and time consuming because the inspection must be performed remotely under water and because most of the rods in the assembly are not on the assembly periphery and thus not readily accessible. It would be far too costly to disassemble, inspect, and reconstitute every assembly suspected of containing one or more leaking fuel rods. What is needed is a method for quickly inspecting all fuel rods in an assembly to identify those in which cladding has been breached, permitting coolant water to enter the rod.